Abstract: The disposed substrate bias generator comprises a capacitor including an electrically insulating film sandwiched between two electrodes one of which is disposed on one main face of a p.sup.- semiconductor substrate through another electrically insulating film, and a first, a second and a third N.sup.+ semiconductor region disposed in spaced relationship on the same main face. The first and second regions form a grounded source and a drain of an MOSFET connected to both its gate and one of the electrodes of the capacitor. The second and third regions form a source and a drain of another MOSFET connected to both its gate and the other main face of the substrate. A signal is applied to the other electrode of the capacitor.